Antistatic laminated polyester film

ABSTRACT

An antistatic film having an antistatic coating film on at least one surface of a polyester film, the antistatic coating film comprising a polymer having a polymerized unit represented by the following formula (1): 
                         
wherein R 1  and R 2  each independently represent a hydrogen atom or a methyl group, R 3  represents an alkylene group having 2 to 10 carbon atoms, R 4  and R 5  each independently represent an alkyl group having 1 to 5 carbon atoms, R 6  represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a hydroxyalkyl group having 2 to 10 carbon atoms, and Y −  represents a halogen ion, a halogenated alkyl ion, a nitrate ion, a sulfate ion, an alkyl sulfate ion, a sulfonate ion or an alkyl sulfonate ion. The film is used in such applications requiring an antistatic property such as a protective film for a liquid crystal polarizing plate.

TECHNICAL FIELD

The present invention relates to an antistatic film and variousfunctional films using the same as a base film. More specifically, itrelates to an antistatic film which is excellent in such properties asan antistatic property, back transferability, abrasion resistance, ananti-blocking property, recoverability and printability and is usefulfor a film for protecting a polarizing plate for a liquid crystal, areproduction film, an electronic material, an OHP film, a packing film,a label, a magnetic card (e.g., a telephone card or a prepaid card) andthe like, and various functional films using the same as a base film,such as those described above.

BACKGROUND ART

Films comprising polyesters such as a polyethylene terephthalate and apolyethylene-2,6-naphthalate have been widely used for generalindustrial materials such as a reproduction film, an electronicmaterial, an OHP film, a packing film, a label and a magnetic card andmagnetic recording materials such as a magnetic tape. As polyesterfilms, films comprising a polyethylene terephthalate or polyethylenenaphthalate having excellent water resistance, chemical resistance,mechanical strength, dimensional stability and electric properties havebeen used or studied. However, the polyester films have a problem ofbeing liable to be electrically charged. When the film is electricallycharged, dust is stuck on the surfaces thereof, resulting in degradationin quality. Further, when an organic solvent is used in a filmprocessing step, there is a risk that electric discharge from theelectrically charged film may cause fire.

As a measure for solving such problems caused by electrical charge, amethod comprising kneading an anionic compound such as an organicsulfonate group, metal powder, carbon powder or the like into thepolyester film and a method comprising depositing a metal compound onthe surfaces of the polyester film are proposed and practically used.However, such methods have problems that the transparency of the film isdegraded and that processing costs are high.

Further, as other methods, various methods for forming an antistaticcoating film on the surface of the film are proposed and practicallyused. Although low-molecular-weight antistatic agents and polymerantistatic agents are known as an antistatic agent to be contained inthe antistatic coating film, they both have advantages anddisadvantages. Thus, an appropriate antistatic agent is selected andused according to application purposes.

JP-A 4-28728 (the term “JP-A” as used herein means an “unexaminedJapanese patent application”) discloses, as a low-molecular-weightantistatic agent, a surfactant-type anionic antistatic agent such as along chain alkyl compound having a sulfonate group. Further, JP-A3-255139 and JP-A 5-320390 disclose, as polymer antistatic agents, apolymer having an ionized nitrogen element in the principal chain and asulfonate-group-modified polystyrene.

However, an antistatic coating film using a low-molecular-weightantistatic agent has a problem that a portion of the antistatic agentmoves in the coating film, concentrates near the interface and moves tothe opposite surface of the film, or antistatic property deteriorates astime passage. Meanwhile, an antistatic coating film using a polymerantistatic agent is not economical because it must contain theantistatic agent in a large amount or have a large thickness so as toattain a good antistatic property. Further, when film chippings unableto be used in products, e.g., film edges cut off and removed in aproduction process are collected and used as recycled materials for filmproduction, coating film components contained in the recycled materialsare thermally degraded during melt film production, and a significantlycolored film which lacks in practicality and therefore has poorrecoverability is obtained. In addition, there occur such a problem thatthe films have blocking therebetween and are difficult to separate fromeach other or the coating films are liable to be abraded, and solutionsfor the problems are desired.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an antistatic filmwhich can solve the problems of the prior art, i.e., an antistatic filmon which an antistatic coating film can be formed at low processingcosts without a pretreatment such as a corona discharge treatment andwhich has an excellent antistatic property, back transferability,abrasion resistance, anti-blocking property and recoverability.

Another object of the present invention is to provide a film to belaminated on a liquid crystal polarizing plate, a film for a label or afilm for a magnetic card, the films using the antistatic film of thepresent invention which has excellent properties including an antistaticproperty as described above as a base film and taking advantages of theproperties.

Other objects and advantages of the present invention will becomeapparent from the following description.

According to the present invention, firstly, the above objects andadvantages of the present invention are achieved by an antistatic filmcomprising a polyester film and an antistatic coating film formed on atleast one surface of the polyester film, the antistatic coating filmcomprising a polymer having a polymerized unit represented by thefollowing formula (1):

wherein R¹ and R² each independently represent a hydrogen atom or amethyl group, R³ represents an alkylene group having 2 to 10 carbonatoms, R⁴ and R⁵ each independently represent an alkyl group having 1 to5 carbon atoms, R⁶ represents a hydrogen atom, an alkyl group having 1to 5 carbon atoms or a hydroxyalkyl group having 2 to 10 carbon atoms,and Y⁻ represents a halogen ion, a halogenated alkyl ion, a nitrate ion,a sulfate ion, an alkyl sulfate ion, a sulfonate ion or an alkylsulfonate ion.

According to the present invention, secondly, the above objects andadvantages of the present invention are achieved by a film to belaminated on a liquid crystal polarizing plate, the film comprising theabove antistatic film of the present invention, an adhesive layer on onesurface of the antistatic film, and a temporarily existing layer on thesurface of the adhesive layer.

According to the present invention, thirdly, the above objects andadvantages of the present invention are achieved by a film for a label,the film comprising the above antistatic film of the present inventionand an ultraviolet curing ink layer or a thermosetting ink layer on thesurface of the antistatic coating film of the antistatic film.

According to the present invention, fourthly, the above objects andadvantages of the present invention are achieved by a film for amagnetic card, the film comprising the above antistatic film of thepresent invention, a magnetic layer on the surface of the antistaticcoating film of the antistatic film, and an ultraviolet curing ink layeron the other surface of the antistatic film.

THE PREFERRED EMBODIMENT OF THE INVENTION

Detailed Description of the present invention will be describedhereinafter.

Polyester

The polyester of the polyester film in the present invention is a linearsaturated polyester comprising a dicarboxylic acid component and aglycol component.

Illustrative examples of the dicarboxylic acid component includeterephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid,hexahydroterephthalic acid, 4,4′-diphenyl dicarboxylic acid, adipicacid, sebacic acid, and dodecane dicarboxylic acid. Terephthalic acidand 2,6-naphthalene dicarboxylic acid are particularly preferred fromthe viewpoint of the mechanical properties of the film.

Illustrative examples of the glycol component include ethylene glycol,diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol,neopentyl glycol, 1,6-hexanediol, cyclohexane dimethanol, and apolyethylene glycol. Ethylene glycol is particularly preferred from theviewpoint of the stiffness of the film.

Of these polyesters, a polyethylene terephthalate and apolyethylene-2,6-naphthalate are preferred because they give a filmhaving excellent mechanical properties such as a high Young's modulusand excellent thermal properties such as thermal dimensional stability.

The above polyester may be a copolyester copolymerized with the abovedicarboxylic acid component or glycol component as a third component.The polyester may be a polyester copolymerized with a polycarboxylicacid component or polyol component having at least three functionalgroups in such a small amount that the polyester is substantiallylinear, e.g. 5 mol % or smaller.

The polyester may be produced in the usual manner. The polyesterpreferably has an intrinsic viscosity of 0.45 dl/g or higher because thefilm has good mechanical properties such as high rigidity.

The polyester film in the present invention may comprise two types ofparticles, i.e., first particles and second particles. The firstparticles and the second particles comprise preferably of differentchemical species. In that case, for example, both particles may comprisean organic material or inorganic material and, in another example, oneof them comprises an organic material and the other comprises aninorganic material.

Illustrative examples of the first particles and the second particlesinclude inorganic particles such as silica, alumina, calcium carbonate,calcium phosphate, talc, zeolite and kaolin, and organic particlescomprising heat-resistant polymers such as a cross-linked polystyrene, across-linked acrylic resin and a cross-linked silicone. Of theparticles, synthetic silica particles, cross-linked silicone particlesand alumina particles are particularly preferred so as to attain hightransparency and high slipperiness. The average particle diameter of thefirst particles is preferably 0.8 to 2.5 μm, more preferably 1.0 to 2.0μm, and the average particle diameter of the second particles ispreferably 0.05 to 0.4 μm, more preferably 0.08 to 0.35 μm. By these twotypes of particles having different average particle diameters, theslipperiness and transparency of the film can be balanced. For instance,even if only the first particles are added, the surface of the filmlacks enough small projections to roughen the surface, resulting in finescratches. Meanwhile, when only the second particles are added, theparticle diameters are so small that the slipperiness of the film is notimproved.

The polyester film in the present invention contains first particleshaving an average particle diameter of 0.8 to 2.5 μm in an amount ofpreferably 0.001 to 0.1 wt %, more preferably 0.005 to 0.1 wt %,particularly preferably 0.008 to 0.07 wt %, from the viewpoint ofbalance between the slipperiness and transparency of the film. Further,the polyester film contains second particles having an average particlediameter of 0.05 to 0.4 μm in an amount of preferably 0.1 to 0.8 wt %,more preferably 0.1 to 0.6 wt %, particularly preferably 0.1 to 0.4 wt%.

The particle size distribution of the particles used in the presentinvention is sharp; for example, the standard deviation of the averageparticle diameter is preferably 0.001 to 0.5, more preferably 0.001 to0.3, particularly preferably 0.001 to 0.2. That is, in the polyesterfilm of the present invention, as described above, it is desirable thatparticles having an average particle diameter which is out of the abovespecific average particle ranges be contained not at all or contained aslittle as possible. Although particles having broad particle sizedistribution cannot be determined from the average particle diameterthereof, particles having particle diameters which rather deviate fromthe average particle diameter are actually also contained,disadvantageously.

The above particles are added to a reaction system, preferably as slurryof glycol, generally at the time of reaction for forming the polyester,e.g., at any time during an ester interchange reaction or apolycondensation reaction when an ester interchange method is used or atany time when a direct polymerization method is used. The particles arepreferably added to the reaction system as a slurry of glycol,particularly during the initial stage of the polycondensation reaction,e.g., before the intrinsic viscosity reaches about 0.3.

The polyester film in the present invention preferably has 0 to 10, morepreferably 0 to 7, particularly preferably 0 to 5 coarse projectionshaving a height of 0.58 μm or higher per 10 cm² of the surface of thefilm. Thereby, adhesion to, for example, an adhesive layer which may belaminated on the film can be improved, and set-off to a processing layercan be prevented, for example.

In addition to the above fine particles, the polyester film in thepresent invention can contain a coloring agent, a known antistaticagent, an organic lubricant, a catalyst, a stabilizer, an antioxidant,an ultraviolet absorber, a fluorescent brightening agent, and otherresins such as a polyethylene, a polypropylene, an ethylene-propylenecopolymer and an olefinic ionomer as required.

The polyester film in the present invention may be a single-layer filmor a laminated film.

Preferred as a laminated polyester film in the present invention is alaminated film formed by stretching an unstretched film obtained by acoextrusion method comprising melt-coextruding all film layers from adie of an extruder and then heat-treating the stretched film. Thelaminated polyester film may be a laminated film comprising two layersor a multilayer film comprising three or more layers.

It is to be understood that when the above laminated polyester filmcontains the first particles and the second particles, it contains theparticles in a layer which forms at least one outermost layer.

When the outermost layer containing these particles is referred to as“layer A”, the layer A is formed on at least one side of the laminatedfilm. However, it may be formed on both sides of the film. When theparticles are contained in the outermost layers on both sides of thelaminated film, the types and contents of the particles may be the sameor different. Therefore, the laminated polyester film may be, forexample, a laminated film having an A/B-type two-layer structure orA/B/A-type three-layer structure using two polymers, a laminated filmhaving a three-layer structure using three polymers such as an A/B/A′type or a laminated film comprising four or more layers using two ormore polymers such as an A/B/C/B/A type or an A/B/A/B/A type. Polyestersconstituting inner layers such as the layer B and the layer C may be thesame as or different from a polyester constituting the layer A but ispreferably the same as the polyester constituting the layer A. Further,the polyester films constituting the inner layers may or may not containthe particles. However, when the polyester films contain the particles,the content of the particles in the polyester films is preferably lowerthan the content of the particles in the layer A. Further, the innerlayers may be formed from melts of recovered polyester films.

The thickness of the polyester film in the present invention ispreferably 20 to 500 μm, more preferably 50 to 450 μm, particularlypreferably 75 to 300 μm, regardless of whether it is a single-layer filmor a laminated film. When the thickness is smaller than 20 μm, the filmhas poor elasticity, while when the thickness is too large, e.g., largerthan 500 μm, film formability is liable to be poor disadvantageously. Asa film to be laminated on a liquid crystal polarizing plate, thethickness of the film is preferably 10 to 100 μm, more preferably 10 to75 μm, particularly preferably 10 to 50 μm. When the thickness issmaller than 10 μm, the film has poor elasticity, while when thethickness is too large, e.g., larger than 100 μm, film formability ispoor and the elasticity of the film is so high that it may damage apolarizing plate when removed disadvantageously.

Antistatic Coating Film

The antistatic film of the present invention has an antistatic coatingfilm on at least one surface of the polyester film. This coating film isformed by applying a coating solution containing an antistatic agent onthe polyester film, stretching the coated film and drying the filmbefore, after or during stretching.

An antistatic agent (hereinafter may be referred to as “antistatic agent(A)”) used in the present invention is a polymer having a polymerizedunit (A1) represented by the following formula (1):

wherein R¹ and R² each independently represent a hydrogen atom or amethyl group, R³ represents an alkylene group having 2 to 10 carbonatoms, R⁴ and R⁵ each independently represent an alkyl group having 1 to5 carbon atoms, R⁶ represents a hydrogen atom, an alkyl group having 1to 5 carbon atoms or a hydroxyalkyl group having 2 to 10 carbon atoms,and Y⁻ represents a halogen ion, a halogenated alkyl ion, a nitrate ion,a sulfate ion, an alkyl sulfate ion, a sulfonate ion or an alkylsulfonate ion.

Y⁻ in the above formula (1) is preferably an alkyl sulfonate ionrepresented by R⁹SO₃ ⁻, (wherein R⁹ is a saturated hydrocarbon grouphaving 1 to 5 carbon atoms) and is particularly preferably CH₃SO₃ ⁻,C₂H₅SO₃ ⁻ or C₃H₇SO₃ ⁻. Further, a polymer having a polymerized unit(A1) represented by the formula (1) wherein R³ is a propylene group andR⁶ is H is preferred because it provides the coating film with goodadhesion to the polyester film, good heat resistance, and an excellentantistatic property in particular.

Preferably, the above polymer can further contain a polymerized unit(A2) derived from a reactive acrylic monomer in addition to thepolymerized unit represented by the above formula (1).

The reactive acrylic monomer refers to an acrylic monomer capable ofreaction such as self-crosslinking by heat and is preferablyN-methoxymethyl acrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, N-methylol methacrylamide or the like.

The ratio between the polymerized unit (A1) and the polymerized unit(A2) derived from the reactive acrylic monomer is preferably (A1)=50 to95 mol % and (A2)=50 to 5 mol %, more preferably (A1)=70 to 95 mol % and(A2)=30 to 5 mol %. In this case, the coating film has good adhesion tothe polyester, good heat resistance and good abrasion resistance, and anexcellent antistatic property in particular.

The polymerized units (A1) and (A2) constitute, for example, 70 to 100mol %, preferably 80 to 100 mol % of all recurring units.

The above polymer comprising the polymerized units (A1) and (A2) can bepreferably produced by the following method, for example. That is, to a1-liter four-neck flask equipped with a thermometer, an agitator, adropping funnel and a Dean Stark diversion device, 400 ml of xylene, 150g of acrylic acid/N-methylol acrylamide (acrylic acid/N-methylolacrylamide=50/50) and 1.0 g of paratoluenesulfonic acid are added.

Then, 21.1 g of N,N-dimethylaminopropylamine is added thereto, theresulting mixture is heated to 140° C. by use of an oil bath, producedwater is continuously removed by azeotropy with xylene, the mixture isallowed to further react at 140° C. for 17 hours, and the amidationreaction is continued until no more water is produced and azeotropy ofwater is no longer observed.

458 g of the obtained reaction product is cooled to 80° C., and 31.1 gof dimethyl sulfate is gradually dropped to the reaction mixture throughthe dropping funnel over 1 hour. During this period, generation of heatis observed, but the reaction temperature is kept at 90° C. by cooling.After completion of dropping, an aging reaction is carried out at 100°C. for 4 hours. The thus obtained reaction product is charged into alarge amount of methanol, and the produced precipitate is collected anddried so as to obtain a polymer antistatic agent.

Further, the polymer used in the present invention can preferablyfurther contain a polymerized unit (A3) represented by the followingformula (2):

wherein R⁷ and R⁸ each independently represent a hydrogen atom or analkyl group having 1 to 5 carbon atoms, and Y⁻ is the same as definedwith respect to the above formula (1), in addition to the polymerizedunit (A1) represented by the above formula (1).

The ratio between the polymerized unit (A1) and the polymerized unit(A3) is preferably the polymerized unit (A1)=50 to 90 mol % and thepolymerized unit (A3)=50 to 10 mol %, more preferably the polymerizedunit (A1)=70 to 90 mol % and the polymerized unit (A3)=30 to 10 mol %.In this case, the coating film has good adhesion to the polyester andgood heat resistance, and an excellent antistatic property inparticular.

The above polymer comprising the polymerized units (A1) and (A3) can bepreferably produced by the following method, for example. That is, itcan be produced by subjecting an acrylic ester monomer anddiallylmethylamine to emulsion polymerization so as to form apolyacrylate-pyrrolidium copolymer having a weight average molecularweight of 2,000 to 100,000, then reacting the copolymer withN,N-dialkylaminoalkylamine such as N,N-dimethylaminopropylamine orN,N-diethylaminopropylamine so as to amidate it, and finally carryingout a quaternary hydroxyalkylation reaction thereby introducing aquaternary cation pair.

The average molecular weight (number average molecular weight) of theabove polymer as the antistatic agent (A) is preferably 3,000 to300,000, more preferably 5,000 to 100,000. When the average molecularweight is lower than 3,000, the back transferability of the antistaticagent is liable to deteriorate, while when the average molecular weightis higher than 300,000, the viscosity of the aqueous coating solutionbecomes so high that the coating solution is difficult to apply to thefilm uniformly disadvantageously.

Binder Resin

In addition to the above antistatic agent (A), the antistatic coatingfilm in the present invention preferably contains a binder resin (B) soas to further improve adhesion to the polyester film. Illustrativeexamples of the binder resin include a polyester resin (B-1) such as acopolyester and an acrylic resin (B-2) such as an acrylic copolymer.These resins can be used alone or in combination of two or more. Use ofthe acrylic resin (B-2), especially an acrylic resin having a glasstransition temperature of −10 to 50° C., is preferred because adhesionbetween the antistatic coating film and the polyester film becomesparticularly good.

The polyester resin (B-1) is preferably a copolyester resin.

Illustrative examples of an acid component constituting the copolyesterresin include terephthalic acid, isophthalic acid, phthalic acid,2,6-naphthalene dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid,adipic acid, sebacic acid, phenylindane dicarboxylic acid, and dimeracid. These components can be used alone or in combination of two ormore. Together with these components, unsaturated polybasic acids suchas maleic acid, fumaric acid and itaconic acid and hydroxycarboxylicacids such as p-hydroxybenzoic acid and p-(β-hydroxyethoxy)benzoic acidcan be used in a small amount. The amount of the unsaturated polybasicacid component or hydroxycarboxylic acid component is preferably as highas 10 mol %, more preferably not larger than 5 mol %. Meanwhile,illustrative examples of a diol component include ethylene glycol,1,4-butanediol, neopentyl glycol, diethylene glycol, dipropylene glycol,1,6-hexanediol, 1,4-cyclohexane dimethanol, xylylene glycol, dimethylolpropionic acid, glycerine, trimethylolpropane, poly(ethyleneoxy)glycol,and poly(tetramethyleneoxy)glycol. These can be used alone or incombination of two or more.

Of these diol components, ethylene glycol, 1,4-butanediol and neopentylglycol are preferred, and ethylene glycol is particularly preferred.

The above copolyester resin can be copolymerized with a slight amount ofa sulfonate-group-containing compound or carboxylate-group-containingcompound so as to facilitate preparation of an aqueous liquid, i.e., anaqueous solution or an aqueous dispersion. The copolymerization ispreferred.

Preferred examples of the sulfonate-group-containing compound includealkali metal sulfonate based or amine sulfonate based compounds such as5-sodium sulfoisophthalate, 5-ammonium sulfoisophthalate, 4-sodiumsulfoisophthalate, 4-methyl ammonium sulfoisophthalate, 2-sodiumsulfoisophthalate, 5-potassium sulfoisophthalate, 4-potassiumsulfoisophthalate, 2-potassium sulfoisophthalate, and sodiumsulfosuccinate. Illustrative examples of thecarboxylate-group-containing compound include trimellitic anhydride,trimellitic acid, pyromellitic anhydride, pyromellitic acid, trimesicacid, cyclobutanetetracarboxylic acid, dimethylol propionic acid, andmonoalkali metal salts thereof. A free carboxyl group is formed into acarboxylate group by the action of an alkali metal compound or an aminecompound after copolymerization.

The above copolyester resin (B-1) can also be used as a modified blockpolymer or modified graft polymer obtained by modifying the abovecopolyester with an acrylic resin, polyurethane resin, silicone resin,epoxy resin, phenol resin or the like.

The copolyester resin can be produced by a conventionally known or usedpolyester producing technique. For example, it can be produced by amethod comprising subjecting 2,6-naphthalene dicarboxylic acid or anester forming derivative thereof such as dimethyl ester, isophthalicacid or an ester forming derivative thereof such as dimethyl ester andtrimellitic anhydride to a neopentyl glycol reaction with ethyleneglycol so as to form a monomer or oligomer, subjecting the monomer oroligomer to a polycondensation reaction under vacuum so as to form acopolyester having a given intrinsic viscosity (intrinsic viscositymeasured at 35° C. by use of o-chlorophenol of 0.2 to 0.8 is preferred),and reacting a free carboxyl group with an alkali compound or aminecompound so as to form a salt. In that case, catalysts for acceleratingthe reactions, e.g., an esterification or transesterification catalystand a polycondensation catalyst, are preferably used, and it is alsopossible to add various additives such as a stabilizer.

The above acrylic resin (B-2) is preferably an acrylic copolymer, forexample. Illustrative examples of components constituting the acryliccopolymer include acrylic acid, methyl acrylate, ethyl acrylate, butylacrylate, sodium acrylate, ammonium acrylate, 2-hydroxyethyl acrylate,methacrylic acid, methyl methacrylate, ethyl methacrylate, butylmethacrylate, sodium methacrylate, ammonium methacrylate, 2-hydroxyethylmethacrylate, glycidyl methacrylate, acryl methacrylate, sodium vinylsulfonate, sodium methallyl sulfonate, sodium styrene sulfonate,acrylamide, methacrylamide, and N-methylol methacrylamide. Thesemonomers can be used in combination with other unsaturated monomers suchas styrene, vinyl acetate, acrylonitrile, methacrylonitrile, vinylchloride, vinylidene chloride and divinylbenzene.

Further, the above acrylic copolymer can also be used as a modifiedblock polymer or modified graft polymer obtained by modifying the aboveacrylic copolymer with a polyester resin, polyurethane resin, siliconeresin, epoxy resin, phenol resin or the like.

Further, binder resins other than those described above can also beadded to the antistatic coating film in the present invention so as toadjust adhesion between the coating film and the polyester film.Illustrative examples of the resins include a polyurethane resin, anepoxy resin, a vinyl resin, a polyether resin and a water soluble resin.

The binder resin (B) is particularly preferably an acrylic resin havinga glass transition temperature of −10 to 50° C. The acrylic resinprovides the antistatic coating film with excellent adhesion to the basefilm and an excellent anti-blocking property, heat resistance andantistatic property at low humidity.

Surfactant

The antistatic coating film in the present invention preferably containsa surfactant so as to have high adhesion to the polyester film and agood anti-blocking property of an antistatic laminated film.Illustrative examples of the surfactant include nonionic surfactantssuch as an alkylene oxide homopolymer, an alkylene oxide copolymer, analiphatic alcohol•alkylene oxide adduct, a long-chain aliphaticsubstituted phenol•alkylene oxide addition polymer, a polyhydric alcoholaliphatic ester and a long-chain aliphatic amide alcohol, and cationicor anionic surfactants such as a compound containing a quaternaryammonium salt, a compound containing an alkylpyridinium salt and acompound containing a sulfonate. The nonionic surfactant is particularlypreferred because it has an excellent effect on adhesion between thecoating film and the base film and the anti-blocking property of theantistatic polyester film.

Polymer Having Oxazoline Group

The antistatic coating film preferably contains a polymer having anoxazoline group. The polymer having an oxazoline group is preferablywater soluble, has a glass transition temperature of 50 to 120° C. andhas an oxazoline equivalent of 80 to 250 g/equivalent. In particular,the polymer is more preferably a polymer comprising methyl methacrylateor methacrylamide as a copolymerization component.

The polymer containing an oxazoline group can be produced bypolymerizing, for example, an addition-polymerizableoxazoline-group-containing monomer alone or together with other monomer.

Illustrative examples of the addition-polymerizableoxazoline-group-containing monomer include 2-vinyl-2-oxazoline,2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline,2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and2-isopropenyl-5-ethyl-2-oxazoline. These may be used alone or inadmixture of two or more. Of these, 2-isopropenyl-2-oxazoline isindustrially easy to obtain and suitable.

The other monomer may be any monomer which can be copolymerized with theaddition-polymerizable oxazoline-group-containing monomer. Illustrativeexamples thereof include (meth)acrylates such as an alkyl acrylate andalkyl methacrylate (wherein the alkyl group is a methyl group, ethylgroup, n-propyl group, isopropyl group, n-butyl group, isobutyl group,t-butyl group, 2-ethylhexyl group or cyclohexyl group); unsaturatedcarboxylic acids such as acrylic acid, methacrylic acid, itaconic acid,maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid andsalts thereof (such as a sodium salt, potassium salt, ammonium salt andtertiary amine salt); unsaturated nitriles such as acrylonitrile andmethacrylonitrile; unsaturated amides such as acrylamide,methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N,N-dialkylacrylamide and N,N-dialkyl methacrylate (wherein the alkyl group is amethyl group, ethyl group, n-propyl group, isopropyl group, n-butylgroup, isobutyl group, t-butyl group, 2-ethylhexyl group or cyclohexylgroup); vinyl esters such as vinyl acetate and vinyl propionate; vinylethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins suchas ethylene and propylene; halogen-containing α,β-unsaturated monomerssuch as vinyl chloride, vinylidene chloride and vinyl fluoride; andα,β-unsaturated aromatic monomers such as styrene and α-methylstyrene.These monomers may be used alone or in combination of two or more.

As melamine, compounds obtained by reacting a methylol melaminederivative obtained by condensing melamine and formaldehyde with a loweralcohol such as methyl alcohol, ethyl alcohol or isopropyl alcohol foretherification and mixtures thereof are preferred. Illustrative examplesof the methylol melamine derivative include monomethylol melamine,dimethylol melamine, trimethylol melamine, tetramethylol melamine,pentamethylol melamine and hexamethylol melamine.

Composition Ratio of Coating Film

The coating solution used for forming the antistatic coating film in thepresent invention preferably comprises an aqueous coating solution ofsolid composition that comprises 10 to 90 wt % of the antistatic agent(A) and 10 to 90 wt % of the binder resin (B) based on 100 wt % of thesolid composition of the coating solution.

More preferably, the coating solution comprises an aqueous coatingsolution of solid composition that comprises 15 to 85 wt % of theantistatic agent (A), 10 to 85 wt % of the binder resin (B) and 1 to 15wt % of surfactant based on 100 wt % of the solid composition of thecoating solution.

When the amount of the antistatic agent (A) is 15 to 85 wt %, goodadhesion between the coating film and the polyester film and a goodantistatic property are attained. When the amount of the binder resin(B) is 10 to 85 wt %, a good antistatic property and good adhesionbetween the coating film and the polyester film are attained. When theamount of the surfactant is 1 to 15 wt %, good adhesion between thecoating film and the polyester film and good anti-blocking property ofthe antistatic film are attained. Thus, these amounts are preferred.

Further, the coating solution particularly preferably comprises anaqueous coating solution of solid composition that comprises 20 to 80 wt% of the antistatic agent (A), 15 to 70 wt % of the binder resin (B), 1to 15 wt % of surfactant and 3 to 25 wt % of the polymer having anoxazoline group based on 100 wt % of the solid composition of thecoating solution.

The amount of the polymer (D) having an oxazoline group is preferably 3to 25 wt % because the coating film shows good solvent resistance andgood durability.

Aqueous Coating Solution

The coating film in the present invention is formed by applying anaqueous coating solution which comprises a composition comprising theabove components to at least one surface of the polyester film andstretching the coated film. The coating film formed from the aqueouscoating solution is dried before and/or after and/or during stretching.The coating solution to be used is an aqueous coating solution havingthe composition comprising the above components dissolved and/ordispersed in water which is a medium. The aqueous coating solution maycontain a slight amount of an organic solvent to aid the stability ofthe coating solution. Illustrative examples of the organic solventinclude methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran,dioxane, cyclohexanone, n-hexane, toluene, xylene, methanol, ethanol,n-propanol, and isopropanol. One or more organic solvents may becontained.

In the present invention, the coating film is preferably formed by useof the aqueous coating solution having the above composition. To theaqueous coating solution, a lubricant is preferably added in such anamount that does not impair properties such as an adhesive property, forthe purposes of providing good slipperiness to the surface of thecoating film and a good anti-blocking property to the film.

Preferred examples of the lubricant include fine particles of apolystyrene resin, acrylic resin, melamine resin, silicone resin,fluorocarbon resin, urea resin, benzoguanamine resin, polyamide resin orpolyester resin. The fine particles of these resins may be thermoplasticor thermosetting as long as contained in the coating film in the form offine particles. The average particle diameter of the fine particles ispreferably 20 to 80 nm, and the content of the fine particles ispreferably 5 to 20 wt %.

In the present invention, additives such as an ultraviolet absorber,pigment, dye, lubricant, blocking inhibitor, water-soluble polymericresin, crosslinking agent, e.g., oxazoline, melamine, epoxy oraziridine, and other antistatic agents can be contained in the aqueouscoating solution in such an amount that does not impair the object ofthe present invention.

The proportion of solid in the aqueous coating solution in the presentinvention is preferably not higher than 30 wt %, more preferably 0.5 to30 wt %. When the proportion is lower than 0.5 wt %, coatability to thepolyester film is liable to be poor, while when the proportion is higherthan 30 wt %, the appearance of the coating film is liable todeteriorate disadvantageously.

Formation of Coating Film

In the present invention, an aqueous coating solution of the above solidcomposition is applied to at least one surface of a polyester film. Thefilm is preferably a polyester film before completion of crystallineorientation. Illustrative examples of the polyester film beforecompletion of crystalline orientation include an unstretched filmprepared by melting a polyester by heating and forming the polyesterinto a film, a monoaxially stretched film prepared by stretching theunstretched film in either the longitudinal direction or the transversedirection, and a biaxially stretched film which is prepared bystretching the unstretched film in both the longitudinal direction andthe transverse direction at low stretch ratios and can be furtherstretched (biaxially stretched film before the film is eventuallyre-stretched in the longitudinal and transverse directions to completecrystalline orientation).

As a method for applying the aqueous coating solution to the polyesterfilm, any known coating can be employed. For example, a roll coatingmethod, a gravure coating method, a microgravure coating method, areverse coating method, a roll brushing method, a spray coating method,an air knife coating method, an impregnation method and a curtaincoating method can be used alone or in combination.

The coating solution is preferably applied in an amount of 0.5 to 50 g,more preferably 2 to 30 g, per m² of running film. The thickness of thecoating film after final drying is preferably 0.01 to 1 μm, morepreferably 0.02 to 0.8 μm. When the thickness of the coating film issmaller than 0.01 μm, the antistatic property becomes unsatisfactory,while when it is larger than 1 μm, the anti-blocking propertydeteriorates disadvantageously. The coating solution may be applied toeither only one surface or both surfaces according to applications ofthe film. A uniform coating film is obtained by drying the coatingsolution after application of the solution.

In the present invention, after the polyester film is coated with theaqueous coating solution, it is dried and preferably subjected to astretch treatment. The drying is preferably carried out at 90 to 130° C.for 2 to 20 seconds. The drying may also serve as a preheating treatmentfor the stretching treatment or a heat treatment at the time ofstretching. The polyester film is preferably stretched to 2.5 to 7 timesin the longitudinal direction and to 2.5 to 7 times in the transversedirection, i.e., to 8 times or more in terms of area ratio, morepreferably 9 to 28 times in terms of area ratio, at a temperature of 70to 140° C. When the film is to be re-stretched, it is preferablystretched at a ratio of 1.05 to 3 times (the area ratio is the same asabove). The heat setting treatment after stretching is preferablycarried out at temperatures higher than the final stretch temperatureand not higher than the melting point for 1 to 30 seconds. For example,a polyethylene terephthalate film is preferably heat-set at 170 to 240°C. for 2 to 30 seconds.

The antistatic film of the present invention has a visible lighttransmittance of 70% or higher and a haze of preferably 8% or lower,more preferably 5% or lower, particularly preferably 4% or lower, forthe sake of good examination of foreign materials in the film. When thehaze is higher than 8%, it is difficult to determine the contents, i.e.,it is difficult to determine foreign materials in the filmdisadvantageously.

The number F of coarse foreign materials of at least 20 μm in size inthe antistatic laminated polyester film of the present inventionpreferably satisfies 0≦F≦10, more preferably 0≦F≦5, particularlypreferably 0≦F≦3 (number of foreign materials per m²). When the numberof the coarse foreign materials is larger than 10 per m², defects inproducts may be overlooked or misdetected during defect examinationafter processing, that is, product inspection may become difficult tocarry out with good accuracy disadvantageously.

To reduce the above number of coarse foreign materials to 10 or less perm², a nonwoven type filter made of stainless steel thin wires having awire diameter of not larger than 15 μm and having an average openingsize of 5 to 25 μm, preferably 10 to 20 μm, is preferably used, as afilter at the time of producing the laminated polyester film, to filterout the foreign materials. The effect of filtering out the foreignmaterials is more remarkable when two filters of the above type areused. When the opening size of the filter to be used is smaller than 5μm, pressure and an increase in pressure at the time of filtration arehigh, so that it is difficult to be practically used as a filter from anindustrial standpoint. Further, when the wire diameter is larger than 15μm, coarse particles cannot be collected with an average opening size of5 to 25 μm.

Further, when the antistatic film of the present invention is used inapplications requiring concealment, an antistatic film using a polyesterfilm which contains 5 to 25 wt % of white pigment and has a thickness of20 to 300 μm to attain a sufficient degree of concealment is preferred.

On the antistatic film of the present invention, an adhesive layer maybe formed on one surface thereof, and a protective layer may be formedon the other surface thereof.

That is, according to the present invention, a film to be laminated on aliquid crystal polarizing plate, the film comprising the antistatic filmof the present invention, an adhesive layer on one surface of theantistatic film, and a temporarily existing layer on the surface of theadhesive layer, is also provided.

The above temporarily existing layer may be, for example, a protectivefilm which is removed to laminate the film on a liquid crystalpolarizing plate or a removable film which is removed after laminated ona liquid crystal polarizing plate.

Further, according to the present invention, a film for a label, thefilm comprising the antistatic film of the present invention and anultraviolet curing ink layer or a thermosetting ink layer on the surfaceof the antistatic coating film of the antistatic film, and a film for amagnetic card, the film comprising the antistatic film of the presentinvention, a magnetic layer on the surface of the antistatic coatingfilm of the antistatic film, and an ultraviolet curing ink layer on theother surface of the antistatic film, are also provided.

EXAMPLES

Hereinafter, the present invention will be further described withreference to Examples.

Further, evaluations in the present invention were made in accordancewith the following methods.

A polyethylene terephthalate and a polyethylene naphthalate may beabbreviated as “PET” and “PEN”, respectively.

1. Surface Resistivity (Antistatic Property)

The surface resistivity (Ω/□) of a sample film after a voltage of 500 Vis applied for 1 minute is measured by use of a resistivity measuringdevice of Takeda Riken Co., Ltd. at a measurement temperature of 23° C.and a measurement humidity of 60%. The surface resistivity is preferably3×10¹² [Ω/□] or less, more preferably 3×10¹¹ [Ω/□] or less.

2. Anti-blocking Property

The surface where a laminated coating film is formed and surface whereno laminated coating film is formed of a sample film cut to a width of50 mm were stuck together and treated under a load of 50 kg/cm² at 60°C. and 80% RH for 17 hours. Then, peel strength between the coatedsurface and the uncoated surface is measured, and an anti-blockingproperty is evaluated based on the following criteria.

-   Rank A: Peel Strength≦10 g (good anti-blocking property)-   Rank B: 10 g<Peel Strength≦30 g (rather poor anti-blocking property)-   Rank C: 30 g<Peel Strength (poor anti-blocking property)    3. Back Transferability

The coated surface and uncoated surface of a sample film are stucktogether and treated under a load of 6 kg/cm² at 50° C. and 70% RH for17 hours. Then, the water contact angle (θ: alternative characteristicof back transferability) of the uncoated surface is measured andevaluated based on the following criteria.

-   Rank A: θ≧55° C. (good back transferability)-   Rank B: 55° C.>θ≧48° C. (rather good back transferability)-   Rank C: 48° C.>θ (poor back transferability)

The water contact angle is measured by setting the above sample film ona contact angle measuring device (product of Elmer Co., Ltd.) with theuncoated surface facing upward, dropping a drop of water at atemperature of 23° C., and reading the contact angle of the drop ofwater after 1 minute from the dropping. The water contact angle of afilm without back transferability is 60 to 72° C., the water contactangle of a film with good back transferability is 55° C. or larger, andthe water contact angle of a film with poor back transferability issmaller than 48° C.

4. Abrasion Resistance

A film sample cut to a width of 20 mm is made contact with a cylindricalstainless stationary bar having a diameter of 10 mm on the coating filmside of the film and caused to run 80 meters under a load of 200 g.Then, bloom of the coating film adhered on the bar is observed, andabrasion resistance is evaluated based on the following criteria.

-   Rank A: No bloom is adhered on the bar. (good abrasion resistance)-   Rank B: Bloom is adhered on the bar in small quantity. (rather poor    abrasion resistance)-   Rank C: Bloom is adhered on the bar in large quantity. (poor    abrasion resistance)    5. Degree of Coloration of Reproduced Film (Recoverability)

A film having no coating film is crushed, molten in an extruder at about300° C. and formed into a chip. Then, the obtained chip is molten toprepare a blank film. The degree of coloration of the film is defined as“blank”. Meanwhile, a sample film having a laminated coating film iscrushed, molten in an extruder at about 300° C. and formed into a chip.Then, the obtained chip is molten to prepare a reproduced film. Thedegree of coloration of this film is evaluated based on the followingcriteria.

-   Rank A: The degree of coloration of the film is comparable to that    of blank film.-   Rank B: The film is somewhat colored.-   Rank C: The degree of coloration of the film is so high that the    film lacks practicality.    6. Adhesion of UV Ink

After ultraviolet curing print ink (Flush Dry FDO RED APN of Toyo InkMfg. Co., Ltd.) is printed on the surface where a coating film is formedof a sample film by use of an RI tester (product of MEI SEISAKUJO CO.,LTD.), the printed ink is cured by means of a medium-pressure mercurylamp (80 W/cm, one lamp type; product of Japan Storage Battery Co.,Ltd.) UV curing device to form an UV ink layer having a thickness of 3.0μm. On this UV ink layer, a scotch tape (18 mm in width; product ofNichiban Co., Ltd.) having a length of 15 cm is stuck. A given load isapplied on the tape by a 2-kg manual load roll to fix the tape, and thenone end of the scotch tape is peeled in the 90° C. direction to evaluatepeel adhesion. The adhesion is evaluated based on the followingcriteria.

-   Rank A: The ink layer is not peeled at all. (good ink adhesion)-   Rank B: The ink layer is partially peeled from the coating film in    the form of cohesive failure. (rather good ink adhesion)-   Rank C: The ink layer is peeled from the coating film in the form of    a layer. (poor ink adhesion)    7. Oxazoline Equivalent

A solution of a polymer containing oxazoline is freeze-dried andanalyzed by ¹H-MNR. An oxazoline equivalent is calculated from anabsorption peak intensity derived from an oxazoline group and absorptionpeak intensities derived from other monomers.

8. Secondary Transition Point

This is measured at a temperature increasing rate of 20° C./min by useof Thermal Analyst 2000 type differential calorimeter of Du Pont Co.,Ltd.

9. Haze and Coarse Foreign Materials

The haze value of a film is measured by use of NDH2000 integratingsphere type haze meter of Nippon Denshoku Industries Co., Ltd. inaccordance with JIS K-7136.

10. Number of Coarse Foreign Materials

The size and number of foreign materials in a film are determined bymagnifying the film by 20 times by transmission irradiation by use of anuniversal projector and counting the number of foreign materials havinga maximum length of 20 μm or larger as coarse foreign materials. Themeasurement area is 1 m².

11. Number of Coarse Projections

Two films each having a size of 10 cm×10 cm are stuck together andirradiated with sodium D radiation (wavelength: 0.57 nm) fromunderneath, and the height of projections is determined from the numberof interference rings observed. The interference rings each represent aprojection height of 0.29 μm, and the number of projections having twoor more interference rings per unit area is calculated and taken as thenumber of coarse projections.

12. Average Particle Diameter of Particles

Particles are scattered such that they do not overlap as much aspossible. A metal deposition film having a thickness of 200 to 300angstroms is formed thereon by a metal sputtering device. The particlesare observed at 10,000 to 30,000 times by a scanning electronmicroscope. Image processing is conducted by Ruzex 500 of NIRECOCORPORATION, and the average particle diameter is determined from 100particles.

13. Windability (Slipperiness)

Windability (slipperiness) is evaluated based on the following threelevels through a winding step including slit at the time of filmproduction.

-   A: No wrinkles are formed in the film.-   B: Wrinkles are sometimes formed in the film.-   C: Wrinkles are always formed in a portion of or all over the film.    14. Air Release Index

20 film pieces each cut to a size of 8 cm×5 cm are laminated. At thecenter of the film pieces excluding the top film piece, an equilateraltriangular hole having a side of 2 mm is formed, and an air releaseindex (mmHg/hr) per unit time is measured by use of DIGITALBECsmoothness tester (product of Toyo Seiki Seisaku-Sho, Ltd.)

Production of Polymer Antistatic Agent:

To a 1-liter four-neck flask equipped with a thermometer, an agitator, adropping funnel and a Dean Stark diversion device, 400 ml of xylene, 150g of acrylic acid/N-methylol acrylamide (acrylic acid/N-methylolacrylamide=50/50) and 1.0 g of paratoluenesulfonic acid were added.

Then, 21.1 g of N,N-dimethylaminopropylamine was added thereto, theresulting mixture was heated to 140° C. by use of an oil bath, producedwater was continuously removed by azeotropy with xylene, the mixture wasallowed to further react at 140° C. for 17 hours, and the amidationreaction was continued until no more water was produced and azeotropy ofwater was no longer observed.

458 g of the obtained reaction product was cooled to 80° C., and 31.1 gof dimethyl sulfate was gradually dropped to the reaction mixturethrough the dropping funnel over 1 hour. During this period, generationof heat was observed, but the reaction temperature was kept at 90° C. bycooling. After completion of dropping, an aging reaction was carried outat 100° C. for 4 hours. The thus obtained reaction product was chargedinto a large amount of methanol, and the produced precipitate wascollected and dried to obtain an antistatic agent A-1.

Example 1

As a polymer antistatic agent (A-1), a polymer antistatic agentcomprising 95 mol % of unit represented by the following formula (1-2)and 5 mol % of N-methylol acrylamide and having an average molecularweight of 10,000 was prepared.

A polyethylene terephthalate (PET) having an intrinsic viscosity(o-chlorophenol, 35° C.) of 0.65 and comprising 0.01 wt % of crosslinkedsilicone having a particle diameter of 1.2 μm as first particles and0.15 wt % of spherical silica having a particle diameter of 0.3 μm assecond particles was molten and cast on a cooling drum, and the obtainedunstretched film was stretched to 3.6 times in the longitudinaldirection.

As an aqueous solution 1, a 10-wt % aqueous solution of solidcomposition comprising 35 wt % of copolyester (Tg=80° C., averagemolecular weight=21,500) (B-1) formed from terephthalic acid (22 mol %),isophthalic acid (1 mol %), 2,6-naphthalene dicarboxylic acid (65 mol%), 4,4′-diphenyl dicarboxylic acid (12 mol %), ethylene glycol (75 mol%), 1,4-cyclohexane dimethanol (10 mol %) and neopentyl glycol (15 mol%), 60 wt % of the polymer antistatic agent (A-1) and 5 wt % ofpolyoxyethylene lauryl ether (C-1) was prepared.

On one surface of the monoaxially stretched film, 4 g/m² (wet) of theaqueous solution 1 was coated by a microgravure coating method.

After dried, the film was stretched to 3.6 times in the transversedirection and heat-treated at 230° C. to obtain an antistatic polyesterfilm having a thickness of 100 μm. The properties of this film are shownin Table 1.

Example 2

As an acrylic copolymer (B-2), an acrylic copolymer (number averagemolecular weight: 258,000, Tg=22° C.) formed from methyl methacrylate(30 mol %), ethyl acrylate (55 mol %), acrylonitrile (10 mol %) andN-methylol methacrylamide (5 mol %) was prepared.

An antistatic polyester film was obtained in the same manner as inExample 1 except that the acrylic copolymer (B-2) was used in place ofthe copolyester (B-1). The properties of this film are shown in Table 1.

Example 3

As an aqueous solution 2, a 10-wt % aqueous solution of solid componentscomprising 20 wt % of the copolyester (B-1), 25 wt % of the acryliccopolymer (B-2), 50 wt % of the polymer antistatic agent (A-1) preparedin Example 1 and 5 wt % of the polyoxyethylene lauryl ether (C-1) wasprepared.

An antistatic polyester film was obtained in the same manner as inExample 1 except that the aqueous solution 2 was used in place of theaqueous solution 1. The properties of this film are shown in Table 1.

Example 4

As a polymer antistatic agent (A-2), a polymer antistatic agentcomprising 80 mol % of the unit represented by the formula (1-2) and 20mol % of N-methylol acrylamide and having an average molecular weight of12,000 was prepared.

An antistatic polyester film was obtained in the same manner as inExample 2 except that the polymer antistatic agent (A-2) was used inplace of the polymer antistatic agent (A-1). The properties of this filmare shown in Table 1.

Example 5

As a polymer antistatic agent (A-3), a polymer antistatic agentrepresented by the formula (1-3) resulting from substituting [CH₃SO₃ ⁻]of the polymer antistatic agent (A-1) with [C₂H₅SO₃ ⁻] was prepared.

An antistatic polyester film was obtained in the same manner as inExample 2 except that the polymer antistatic agent (A-3) was used inplace of the polymer antistatic agent (A-1). The properties of this filmare shown in Table 1.

Example 6

As a polymer antistatic agent (A-4), a polymer antistatic agentcomprising 90 mol % of unit represented by the following formula (1-4)and 10 mol % of 2-hydroxyethyl methacrylate and having an averagemolecular weight of 15,000 was prepared.

An antistatic polyester film was obtained in the same manner as inExample 2 except that the polymer antistatic agent (A-4) was used inplace of the polymer antistatic agent (A-1). The properties of this filmare shown in Table 1.

Example 7

As an aqueous solution 3, a 10-wt % aqueous solution of solid componentscomprising 83 wt % of the acrylic copolymer (B-2), 17 wt % of thepolymer antistatic agent (A-1) prepared in Example 1 and 5 wt % of thepolyoxyethylene lauryl ether (C-1) was prepared.

An antistatic polyester film was obtained in the same manner as inExample 1 except that the aqueous solution 3 was used in place of theaqueous solution 1. The properties of this film are shown in Table 1.

Example 8

As an aqueous solution 4, a 10-wt % aqueous solution of solid componentscomprising 12 wt % of the acrylic copolymer (B-2), 83 wt % of thepolymer antistatic agent (A-1) prepared in Example 1 and 5 wt % of thepolyoxyethylene lauryl ether (C-1) was prepared.

An antistatic polyester film was obtained in the same manner as inExample 1 except that the aqueous solution 4 was used in place of theaqueous solution 1. The properties of this film are shown in Table 1.

Example 9

As an aqueous solution 5, a 10-wt % aqueous solution of solid componentscomprising 15 wt % of the acrylic copolymer (B-2), 70 wt % of thepolymer antistatic agent (A-1) prepared in Example 1, 10 wt % of polymercontaining an oxazoline group (molecular weight: 100,000, Tg=100° C.,oxazoline equivalent=150 g (solid)/equivalent) (D-1) comprising2-isopropenyl-2-oxazoline (63 mol %), methyl methacrylate (14mol %)andmethacrylamide (23mol %) and 5 wt % of the polyoxyethylene laurylether (C-1) was prepared.

An antistatic polyester film was obtained in the same manner as inExample 1 except that the aqueous solution 5 was used in place of theaqueous solution 1. The properties of this film are shown in Table 1.

Example 10

An antistatic polyester film was obtained in the same manner as inExample 2 except that a polyethylene naphthalate film was used in placeof the polyethylene terephthalate film. The properties of this film areshown in Table 1.

Example 11

A composition comprising 90 wt % of polyethylene terephthalate having anintrinsic viscosity (o-chlorophenol, 35° C.) of 0.65 and 10 wt % oftitanium oxide having an average particle diameter of 0.4 μm was moltenand cast on a cooling drum, and the obtained unstretched film wasstretched to 3.6 times in the longitudinal direction.

As an aqueous solution 7, a 10-wt % aqueous solution of solidcomposition comprising 35 wt % of the acrylic copolymer (B-2), 60 wt %of the polymer antistatic agent (A-1) prepared in Example 1 and 5 wt %of the polyoxyethylene lauryl ether (C-1) was prepared.

On one surface of the monoaxially stretched film, 4 g/m² (wet) of theaqueous solution 7 was coated by a microgravure coating method.

After dried, the film was stretched to 3.6 times in the transversedirection and heat-treated at 230° C. to obtain an antistatic polyesterfilm having a thickness of 188 μm. The properties of this film are shownin Table 1.

Example 12

An antistatic polyester film was obtained in the same manner as inExample 1 except that 0.03 wt % of first particles having a particlediameter of 1.2 μm and 0.24 wt % of second particles having a particlediameter of 0.12 μm were used. The properties of this film are shown inTable 1.

Example 13

An antistatic polyester film was obtained in the same manner as inExample 1 except that a polymer antistatic agent comprising 95 mol % ofthe unit represented by the above formula (1-2) and 5 mol % ofN-methoxymethyl acrylamide and having an average molecular weight of10,000 was used as the polymer antistatic agent (A-1). The properties ofthis film are shown in Table 1.

Comparative Example 1

As an aqueous solution 8, a 10-wt % aqueous solution of solidcomposition comprising 88 wt % of the copolyester (B-1), 7 wt % of thepolymer antistatic agent (A-1) and 5 wt % of polyoxyethylene nonylphenylether (C-2) was prepared.

An antistatic polyester film was obtained in the same manner as inExample 1 except that the aqueous solution 8 was used in place of theaqueous solution 1. The properties of this film are shown in Table 1.

Comparative Example 2

As an aqueous solution 9, a 10-wt % aqueous solution of solidcomposition comprising 95 wt % of the polymer antistatic agent (A-1) and5 wt % of the polyoxyethylene nonylphenyl ether (C-2) was prepared.

An antistatic polyester film was obtained in the same manner as inExample 1 except that the aqueous solution 9 was used in place of theaqueous solution 1. The properties of this film are shown in Table 1.

Comparative Example 3

As an aqueous solution 10, a 10-wt % aqueous solution of solidcomposition comprising 70 wt % of the copolyester (B-1), 25 wt % ofsodium polystyrene sulfonate (A-5) as an antistatic agent and 5 wt % ofthe polyoxyethylene nonylphenyl ether (C-2) was prepared.

An antistatic polyester film was obtained in the same manner as inExample 1 except that the aqueous solution 10 was used in place of theaqueous solution 1. The properties of this film are shown in Table 1.

Comparative Example 4

As an aqueous solution 11, a 10-wt % aqueous solution of solidcomposition comprising 70 wt % of the copolyester (B-1), 25 wt % ofsodium dodecylbenzene sulfonate (A-6) and 5 wt % of the polyoxyethylenenonylphenyl ether (C-1) was prepared.

An antistatic polyester film was obtained in the same manner as inExample 1 except that the aqueous solution 11 was used in place of theaqueous solution 1. The properties of this film are shown in Table 1.

Comparative Example 5

A biaxially stretched polyester film was obtained in the same manner asin Example 1 except that the aqueous solution 1 was not coated. Theproperties of this film are shown in Table 1.

Comparative Example 6

An antistatic laminated polyester film was obtained in the same manneras in Example 1 except that the size of the openings of the filter waschanged from 20 μm to 30 μm. The properties of this film are shown inTable 1.

Comparative Example 7

An antistatic laminated polyester film was obtained in the same manneras in Example 1 except that the average particle diameter and amount ofthe lubricant to be added to PET were changed as shown in Table 1 andthat the size of the openings of the filter was changed from 20 μm to 30μm. The properties of this film are shown in Table 1.

Comparative Example 8

An antistatic laminated polyester film was obtained in the same manneras in Example 1 except that the type, average particle diameter andamount of the lubricant to be added to PET were changed as shown inTable 1. The properties of this film are shown in Table 1.

TABLE 1 Layer Particles Contained Particle Coarse Foreign CoarseThickness Configuration in Surface Layer Diameter Additive MaterialProjection μm A/B/A μm Type of Lubricant μm Wt % Number/10 cm² Number/10cm² Windability Ex. 1 38 2/34/2 Crosslinked Silicone 1.2 0.01 5 1 ASpherical Silica 0.3 0.15 Ex. 2 38 2/34/2 Crosslinked Silicone 1.2 0.015 1 A Spherical Silica 0.3 0.15 Ex. 3 38 2/34/2 Crosslinked Silicone 1.20.01 5 1 A Spherical Silica 0.3 0.15 Ex. 4 38 2/34/2 CrosslinkedSilicone 1.2 0.01 5 1 A Spherical Silica 0.3 0.15 Ex. 5 38 2/34/2Crosslinked Silicone 1.2 0.01 5 1 A Spherical Silica 0.3 0.15 Ex. 6 382/34/2 Crosslinked Silicone 1.2 0.01 5 1 A Spherical Silica 0.3 0.15 Ex.7 38 2/34/2 Crosslinked Silicone 1.2 0.01 5 1 A Spherical Silica 0.30.15 Ex. 8 38 2/34/2 Crosslinked Silicone 1.2 0.01 5 1 A SphericalSilica 0.3 0.15 Ex. 9 38 2/34/2 Crosslinked Silicone 1.2 0.01 5 1 ASpherical Silica 0.3 0.15 Ex. 10 38 2/34/2 Crosslinked Silicone 1.2 0.015 1 A Spherical Silica 0.3 0.15 Ex. 11 38 2/34/2 Crosslinked Silicone1.2 0.01 5 1 A Spherical Silica 0.3 0.15 Ex. 12 38 2/34/2 CrosslinkedSilicone 1.2 0.03 5 1 A Spherical Silica 0.12 0.24 Ex. 13 38 2/34/2Crosslinked Silicone 1.2 0.01 5 1 A Spherical Silica 0.3 0.15 AirRelease Surface Degree of Index Resistivity Anti-blocking Back AbrasionColoration of Adhesion of mmHg/hr Ω/□ Property TransferabilityResistance Reproduced Film UV Ink Ex. 1 16 6 × 10⁸ A A A A A Ex. 2 16 3× 10⁸ A A A A A Ex. 3 16 6 × 10⁸ A A A A A Ex. 4 16 2 × 10⁸ A A A A AEx. 5 16 4 × 10⁹ A A A A A Ex. 6 16 2 × 10⁸ A A A A A Ex. 7 16  1 × 10¹⁰A A A A A Ex. 8 16 7 × 10⁷ B A A B A Ex. 9 16 3 × 10⁸ A A A A A Ex. 1016 4 × 10⁸ A A A A A Ex. 11 16 8 × 10⁸ A A A A A Ex. 12 16 6 × 10⁸ A A AA A Ex. 13 16 6 × 10⁸ A A A A A Layer Particles Contained ParticleCoarse Foreign Coarse Thickness Configuration in Surface Layer DiameterAdditive Material Projection μm A/B/A μm Type of Lubricant μm Wt %Number/10 cm² Number/10 cm² Windability C. Ex. 1 38 2/34/2 CrosslinkedSilicone 1.2 0.01 5 1 A Spherical Silica 0.3 0.15 C. Ex. 2 38 2/34/2Crosslinked Silicone 1.2 0.01 5 1 A Spherical Silica 0.3 0.15 C. Ex. 338 2/34/2 Crosslinked Silicone 1.2 0.01 5 1 A Spherical Silica 0.3 0.15C. Ex. 4 38 2/34/2 Crosslinked Silicone 1.2 0.01 5 1 A Spherical Silica0.3 0.15 C. Ex. 5 38 2/34/2 Crosslinked Silicone 1.2 0.01 5 1 ASpherical Silica 0.3 0.15 C. Ex. 6 38 2/34/2 Crosslinked Silicone 1.20.01 22 6 A Spherical Silica 0.3 0.15 C. Ex. 7 38 2/34/2 CrosslinkedSilicone 1.8 0.006 14 3 B Spherical Silica 0.2 0.4 C. Ex. 8 38 2/34/2Crosslinked Silicone 0.15 0.5 5 3 C Air Release Surface Degree of IndexResistivity Anti-blocking Back Abrasion Coloration of Adhesion ofmmHg/hr Ω/□ Property Transferability Resistance Reproduced Film UV InkC. Ex. 1 16 5 × 10¹³ A A A A A C. Ex. 2 16 6 × 10⁷  C A C B C C. Ex. 316 6 × 10¹⁰ A A C A A C. Ex. 4 16 5 × 10¹⁰ C C A A A C. Ex. 5 16 8 ×10¹⁵ A A A A C C. Ex. 6 16 6 × 10⁸  A A A A A C. Ex. 7 15 6 × 10⁸  A A AA A C. Ex. 8 5 6 × 10⁸  A A A A A Ex.: Example C. Ex.: ComparativeExample

As described above, the antistatic polyester film in the presentinvention has an excellent antistatic property under low humidity,anti-blocking property, back transferability, abrasion resistance andrecoverability as compared with conventional counterparts. It is usefulparticularly as a reproduction film, an electronic material, an OHPfilm, a packing film, a label or a magnetic card (e.g., a telephone cardor a prepaid card).

1. An antistatic film comprising a polyester film and an antistaticcoating film on at least one surface of the polyester film, theantistatic coating film comprising a polymer having a polymerized unitrepresented by the following formula (1):

wherein R¹ and R² each independently represent a hydrogen atom or amethyl group, R³ represents an alkylene group having 2 to 10 carbonatoms, R⁴ and R⁵ each independently represent an alkyl group having 1 to5 carbon atoms, R⁶ represents a hydrogen atom, an alkyl group having 1to 5 carbon atoms or a hydroxyalkyl group having 2 to 10 carbon atoms,and Y⁻ represents a halogen ion, a halogenated alkyl ion, a nitrate ion,a sulfate ion, an alkyl sulfate ion, a sulfonate ion or an alkylsulfonate ion, wherein the polymer further comprises a polymerized unitderived from a reactive acrylic monomer in addition to the polymerizedunit represented by the formula (1), wherein the antistatic coating filmcomprises a binder resin in addition to the polymer, the amounts of thepolymer and the binder resin are 10 to 90 wt % and 10 to 90 wt %,respectively, based on their total and the binder resin is at least oneselected from the group consisting of a polyester resin and an acrylicresin, and wherein the antistatic coating film further comprises 3 to 25parts by weight of polymer having an oxazoline group based on 100 partsby weight of the total of the polymer and the binder resin.
 2. The filmof claim 1, wherein the antistatic coating film is formed by applying acoating solution comprising the polymer having the polymerized unitrepresented by the formula (1) on the polyester film and stretching thepolyester film having the coating film.
 3. The film of claim 1, whereinthe reactive acrylic monomer is at least one selected from the groupconsisting of N-methoxymethyl acrylamide, 2-hydroxyethyl acrylate,2-hydroxyethyl methacrylate and N-methylol methacrylamide.
 4. The filmof claim 1, wherein the molar ratio of the polymerized unit representedby the formula (1) to the polymerized unit derived from the reactiveacrylic monomer is 50:50 to 95:5.
 5. The film of claim 1, wherein thepolymer further comprises a polymerized unit represented by thefollowing formula (2):

wherein R⁷ and R⁸ each independently represent a hydrogen atom or analkyl group having 1 to 5 carbon atoms, and Y⁻ is the same as definedabove, in addition to the polymerized unit represented by the formula(1).
 6. The film of claim 5, wherein the molar ratio of the polymerizedunit represented by the formula (1) to the polymerized unit representedby the formula (2) is 50:50 to 90:10.
 7. The film of claim 1, whereinthe polyester film comprises 0.001 to 0.1 wt % of first particles havingan average particle diameter of 0.8 to 2.5 μm and 0.1 to 0.8 wt % ofsecond particles having an average particle diameter of 0.05 to 0.4 μmand has 0 to 5 projections each having a height of 0.58 μm or higher per10 cm² of a surface of the film.
 8. The film of claim 7, wherein thefirst particles and the second particles comprise different chemicalspecies.
 9. The film of claim 8, wherein one of the first particles andthe second particles comprises an organic material, and the othercomprises an inorganic material.
 10. The film of claim 8, wherein thefirst particles and the second particles comprise an inorganic material.11. The film of claim 1, wherein the antistatic coating film furthercomprises 1 to 15 parts by weight of surfactant based on 100 parts byweight of the total of the polymer and the binder resin.
 12. The film ofclaim 1, wherein the polymer having an oxazoline group is water soluble,has a glass transition temperature of 50 to 120° C. and has an oxazolineequivalent of 80 to 250 g/equivalent.
 13. The film of claim 1, whereinthe polymer having an oxazoline group comprises a polymerized unitderived from methyl methacrylate and a polymerized unit derived frommethacrylamide as copolymerized units.
 14. The film of claim 1, whereinthe acrylic resin as the binder resin has a glass transition temperatureof −10 to 50° C.
 15. The film of claim 1, wherein the polyester film isa single-layer film or a laminated film.
 16. The film of claim 15,wherein the laminated film comprises three layers, and the middle layeris formed from a melt of a recovered polyester film.
 17. The film ofclaim 1, wherein the polyester in the polyester film is a polyethyleneterephthalate or polyethylene-2,6-naphthalene dicarboxylate.
 18. Thefilm of claim 1, having a visible light transmittance of 70% or higherand a haze of 8% or lower.
 19. The film of claim 1, wherein thepolyester film comprises 5 to 25 wt % of white pigment and has athickness of 20 to 300 μm.
 20. A film for laminating on a liquid crystalpolarizing plate, the film comprising the antistatic film of claim 1, anadhesive layer on one surface of the antistatic film, and a temporarilyexisting layer on the surface of the adhesive layer.
 21. The film ofclaim 20, wherein the temporarily existing layer is a protective filmwhich is removed to laminate the film on a liquid crystal polarizingplate or a removable film which is removed after laminated on a liquidcrystal polarizing plate.
 22. A film for a label, the film comprisingthe antistatic film of claim 1 and an ultraviolet curing ink layer or athermosetting ink layer on the surface of the antistatic coating film ofthe antistatic film.
 23. A film for a magnetic card, the film comprisingthe antistatic film of claim 1, a magnetic layer on the surface of theantistatic coating film of the antistatic film, and an ultravioletcuring ink layer on the other surface of the antistatic film.